Design a Layered ASCII Canvas Command Processor

Problem Statement

Design an ASCII canvas system with a fixed width of 10 columns and height of 6 rows. The canvas allows users to place, remove, and reorder rectangular shapes on different layers. Each rectangle is filled with a single ASCII character. When rendered, higher-layer shapes occlude lower-layer shapes. Pixels with no shapes display a default background character '.'. Coordinates use (x, y) where x represents horizontal position (0 <= x < 10, left to right) and y represents vertical position (0 <= y < 6, top to bottom).

Implement a class AsciiCanvas with the following interface:

class AsciiCanvas:
    def __init__(self, width: int = 10, height: int = 6):
        """Initializes the canvas with the given dimensions."""
        pass

    def add_rectangle(self, shape_id: str, x: int, y: int, width: int, height: int, fill: str) -> bool:
        """Adds a new filled rectangle at the top of the layer stack.
        Returns False if shape_id already exists or dimensions are invalid (width  bool:
        """Removes the rectangle with shape_id. Returns False if shape_id does not exist."""
        pass

    def bring_to_front(self, shape_id: str) -> bool:
        """Moves shape_id to the topmost layer. Returns False if shape_id does not exist."""
        pass

    def send_to_back(self, shape_id: str) -> bool:
        """Moves shape_id to the bottommost layer. Returns False if shape_id does not exist."""
        pass

    def render(self) -> list[str]:
        """Returns the rendered 10x6 grid as a list of 6 strings, each of length 10."""
        pass

Example

canvas = AsciiCanvas(10, 6)
canvas.add_rectangle("A", x=1, y=1, width=4, height=3, fill="A")
canvas.add_rectangle("B", x=3, y=2, width=4, height=3, fill="B")

# B is on top of A
print("\n".join(canvas.render()))
# Output:
# ..........
# .AAAA.....
# .AABBBB...
# .AABBBB...
# ...BBBB...
# ..........

canvas.bring_to_front("A")
print("\n".join(canvas.render()))
# Output:
# ..........
# .AAAA.....
# .AAAABB...
# .AAAABB...
# ...BBBB...
# ..........

Expectations

• Separate domain models (e.g., Rectangle, LayerStack, CanvasRenderer) cleanly.
• Explicitly handle edge cases: shapes partially or fully out of bounds, duplicate IDs, non-existent shape operations.
• Discuss the trade-offs between rendering lazily (rasterizing on render()) versus eagerly (maintaining a pixel buffer per operation).